Field of the Invention
The present invention relates to an image forming apparatus which performs printing on a transfer medium based on image data, an image forming system, an image formation control method and an image forming method.
Description of the Related Art
As to an image forming apparatus and an image forming system, an apparatus has been proposed which, when a paper jam (JAM) occurs at a transfer medium being conveyed, enables processing (prepurge processing) for discharging sheets on an upstream side of a position where the paper jam occurs to a tray to which the sheets can be discharged. Because sheets for normal job before image formation are not used even if printing is performed on the sheets because a paper discharge destination is changed and pages are skipped, it is preferable to output blank sheets so as not to waste toner. Further, if blank sheets are outputted, the sheets can be reused. Printing can be performed again on pages on which printing is not performed through JAM recovery.
Further, as to an image forming apparatus and a post-processing apparatus, an apparatus has been proposed which enables processing (output paper concentration adjustment processing) of reading patch concentration of a chart for gamma correction using a mounted concentration sensor, and performing gamma correction processing.
In the correction processing using the chart for gamma correction, upon paper feeding, for example, by notifying a post-processing apparatus side including a reading apparatus that the sheet is a sheet for a chart for correction, the post-processing apparatus side, or the like, specifies a sheet to be conveyed, performs reading using the concentration sensor and notifies a control side of the result. Further, through notification of the reading result and notification of paper discharge completion from the post-processing apparatus, or the like, the control side determines that reading has been normally performed.
However, when a paper jam occurs during correction processing, a blank sheet is conveyed without a chart for correction being printed through prepurge processing. Therefore, the reading apparatus cannot normally read concentration and reports an error, or an image is formed based on an abnormal value, which results in formation of an abnormal image. Further, if processing is performed without correction processing being performed in association with prepurge, the processing is inefficient, and, when an image is printed on a sheet, printing itself is wasted.
Japanese Patent Laid-Open No. 2011-126017 enables image correction using sheets remaining in the apparatus upon occurrence of a paper jam. However, it is not determined whether the remaining sheets are sheets for normal job or sheets for correction, and necessary correction processing for the sheets is not performed, which causes a problem, for example, processing of image correction is performed at unintended time or patches are formed on different types of sheets.
The present invention has been made in view of the above circumstances, and is intended to provide an image forming apparatus which enables reduction of generation of waste paper and efficient correction by continuing image correction in a transfer medium required for image correction, an image forming system, an image formation control method and an image forming method upon occurrence of a paper jam.